This invention relates to a microprogram activity-checking circuit, which is suitable for verifying the validity of test data based on the activity ratio of a microprogram, calculated upon testing of the microprogram.
A microprogram-controlled type data-processing device executes a user command based on a combination of microinstructions or a microprogram. When a user command having complex functions or a complex microprogram is tested, checking the activity and activity ratio of the microprogram under test is a significantly effective method of verifying the validity of test data used for the testing of the microprogram.
When one step of a microprogram is executed, the step is considered to have become active. An activity ratio is the ratio of the number of active steps to the number of the total steps of a microprogram under test. Test data, by nature, should have a 100% activity ratio. Test data with a 100% activity ratio should be easy to prepare when a microprogram to be tested consists of a small number of steps and its logic is simple; however, preparation of such test data is difficult when the microprogram is complex and/or lengthy. It is also difficult to verify the validity of test data which is used to check a complex and lengthy microprogram. Therefore, there is a demand for a microprogram activity-checking circuit which is capable of verifying the validity of such test data easily and reliably.